Method for manufacturing nitride semiconductor device and nitride semiconductor device
A method for manufacturing a nitride semiconductor device including: forming an N-type region in a nitride semiconductor layer; implanting ions of an acceptor element into a region under the N-type region in the nitride semiconductor layer; and forming a first P-type region under the N-type region by subjecting the nitride semiconductor layer to heat treatment and activating the acceptor element. The forming the N-type region includes implanting ions of a donor element into the nitride semiconductor layer such that concentration of the donor element in the N-type region is equal to or greater than concentration of the acceptor element in the first P-type region. The implanting ions of the acceptor element into a region under the N-type region includes implanting ions of the acceptor element such that concentration of the acceptor element in the first P-type region is 1×10 19 cm −3 or more and 1×10 21 cm −3 or less.
1. A method for manufacturing a nitride semiconductor device comprising:
forming a P-type well region in a nitride semiconductor layer;
forming an N-type region within the P-type well region including implanting ions of a donor element into the P-type well region at a first concentration;
implanting ions of an acceptor element at a second concentration into a first P-type region within the P-type well region and located under the N-type region so that the first P-type region is sandwiched by the N-type region and the P-type well region on both sides in a vertical direction so as to be respectively in contact with the N-type region and the P-type well region, and an uppermost surface of the first P-type region is deeper than an uppermost surface of the N-type region, wherein the first concentration is greater than or equal to the second concentration, and the second concentration is 1×10 19 cm −3 or more and 1×10 21 cm −3 or less; and
forming the first P-type region by subjecting the nitride semiconductor layer in which the P-type well region and the N-type region are formed and into which ions of the acceptor element are implanted to heat treatment and activating the acceptor element.
2. The method for manufacturing the nitride semiconductor device according to claim 1 , wherein a maximum temperature of the heat treatment is 1300° C. or more and 2000° C. or less.
3. The method for manufacturing the nitride semiconductor device according to claim 1 further comprising:
implanting ions of the acceptor element at the second concentration into a region sandwiched by the two N-type regions on both sides,
wherein, forming the first P-type region includes,
forming the first P-type region located under the two N-type regions and a second P-type region sandwiched by the two N-type regions on both sides by subjecting the nitride semiconductor layer in which the two N-type regions are formed and ions of the acceptor element are implanted into regions located under the two N-type regions and a region sandwiched by the two N-type regions on both sides to heat treatment and activating the acceptor element, and
forming the N-type region includes,
implanting ions of the donor element into the nitride semiconductor layer at the first concentration.
4. The method for manufacturing the nitride semiconductor device according to claim 3 , wherein
the method simultaneously performs, using a mask arranged on one surface side of the nitride semiconductor layer, implanting ions of the acceptor element into regions located under the two N-type regions, and implanting ions of the acceptor element into a region sandwiched by the two N-type regions on both sides.
5. The method for manufacturing the nitride semiconductor device according to claim 1 further comprising:
forming a through-hole exposing the first P-type region at a bottom surface of the through-hole by removing at least a portion of the N-type region from one surface side of the nitride semiconductor layer; and
forming an electrode in the through-hole and causing the electrode to come into contact with the first P-type region.
6. The method for manufacturing the nitride semiconductor device according to claim 5 , wherein
forming the through-hole includes,
removing a portion of the N-type region to form the through-hole and simultaneously leave another portion of the N-type region unremoved in the nitride semiconductor layer, and
forming the electrode includes:
forming a first portion of the electrode in the through-hole and causing the first portion to come into contact with the first P-type region; and
forming a second portion of the electrode on the one surface side of the nitride semiconductor layer and causing the second portion to come into contact with the another portion of the N-type region.
7. The method for manufacturing the nitride semiconductor device according to claim 6 , wherein
forming the electrode includes,
integrally forming the first portion and the second portion.
8. A nitride semiconductor device comprising:
a nitride semiconductor layer;
an N-type region formed on one surface side of the nitride semiconductor layer;
a P-type well region formed in the nitride semiconductor layer; and
a first P-type region formed within the P-type well region and located under the N-type region so that the first P-type region is sandwiched by the N-type region and the P-type well region on both sides in a vertical direction so as to be respectively in contact with the N-type region and the P-type well region, and an uppermost surface of the first P-type region is deeper than an uppermost surface of the N-type region,
wherein concentration of a donor element in the N-type region has a value equal to or greater than concentration of an acceptor element in the first P-type region, and
concentration of the acceptor element in the first P-type region is 1×10 19 cm −3 or more and 1×10 21 cm −3 or less.
9. The nitride semiconductor device according to claim 8 , wherein thickness of the first P-type region is 1 nm or more and 25 nm or less.
10. The nitride semiconductor device according to claim 8 further comprising:
a second P-type region formed on the one surface side of the nitride semiconductor layer and sandwiched by two N-type regions on both sides,
wherein concentration of the acceptor element in at least a portion of the second P-type region is 1×10 19 cm −3 or more and 1×10 21 cm −3 or less.
11. The nitride semiconductor device according to claim 10 , wherein an interval between portions within the two N-type regions, the portions sandwiching the second P-type region on both sides, is 50 nm or more and 500 nm or less.
12. The nitride semiconductor device according to claim 10 , wherein depths of the two N-type regions from the one surface side of the nitride semiconductor layer and a depth of the second P-type region from the one surface side of the nitride semiconductor layer are equal.
13. The nitride semiconductor device according to claim 10 , wherein
the second P-type region includes:
a first region; and
second regions each of which is located between the first region and one of the two N-type regions and is respectively in contact with the first region and the N-type region, concentration of the acceptor element in the second regions is higher than in the first region, and concentration of the acceptor element in the second regions is 1×10 19 cm −3 or more and 1×10 21 cm −3 or less.
14. The nitride semiconductor device according to claim 13 , wherein density of acceptor segregation in the second regions is lower than density of the acceptor segregation in the first region.
15. The nitride semiconductor device according to claim 14 , wherein
when the acceptor segregation is classified into:
rod-like acceptor segregation having a length in one direction of 30 nm or more and a concentration of the acceptor element of 5×10 20 cm −3 or more; and
non-rod-like acceptor segregation having a length in one direction of less than 30 nm and a concentration of the acceptor element of 5×10 20 cm −3 or more,
in the second regions, density of the rod-like acceptor segregation is equal to or less than 1×10 14 cm −3 , and density of the non-rod-like acceptor segregation is less than 1×10 15 cm −3 .
16. The nitride semiconductor device according to claim 13 , wherein length of each of the second regions in a direction in which the two N-type regions sandwich the second P-type region on both sides is 1 nm or more and 25 nm or less.
17. The nitride semiconductor device according to claim 8 further comprising an electrode formed on the N-type region.
18. The nitride semiconductor device according to claim 8 further comprising an electrode penetrating the N-type region and coming into contact with the first P-type region.
19. The nitride semiconductor device according to claim 18 , wherein
the electrode has:
a first portion arranged in a through-hole penetrating the N-type region and coming into contact with the first P-type region at a bottom surface of the through-hole; and
a second portion arranged on the one surface side of the nitride semiconductor layer and coming into contact with the N-type region.
20. The nitride semiconductor device according to claim 19 , wherein the first portion and the second portion are integrally formed.
21. The nitride semiconductor device according to claim 8 , wherein the nitride semiconductor layer is gallium nitride.
22. The nitride semiconductor device according to claim 8 ,
wherein the acceptor element include at least either magnesium or beryllium.
23. The nitride semiconductor device according to claim 8 comprising:
a field effect transistor formed in the nitride semiconductor layer and having a channel formed in the P-type well region,
wherein the first P-type region has a higher concentration of the acceptor element than the P-type well region and is in contact with the P-type well region.
24. The nitride semiconductor device according to claim 8 comprising:
a diode formed in the nitride semiconductor layer,
wherein the first P-type region is included in the diode.
25. The nitride semiconductor device according to claim 8 , wherein the first P-type region is a P+-type region and causes a connection between an N+-type source region and the P-type well region to be an ohmic connection.